TiDB returns wrong result while comparison between integer and varchar is performed

[PragmaTwice]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE a(b char, c varchar(50));
INSERT a VALUES("", "sc");
CREATE TABLE d(e varchar(0));
INSERT d VALUES("");
SELECT * FROM a WHERE c IN(SELECT b UNION SELECT avg(e) FROM d);

2. What did you expect to see? (Required)

In MySQL:

+------+------+
| b    | c    |
+------+------+
|      | sc   |
+------+------+
1 row in set (0.00 sec)

3. What did you see instead (Required)

Empty set (0.00 sec)

4. What is your TiDB version? (Required)

+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()
                                                                                                                                                 |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v5.2.0-alpha-88-ged52601e6
Edition: Community
Git Commit Hash: ed52601e6eb560138db8cdccdfa1b5e2d33a11f0
Git Branch: master
UTC Build Time: 2021-06-16 13:03:48
GoVersion: go1.16.4
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)